The invention relates to pipe couplings of the kind comprising a first pipe-encircling member, a sealing element disposed within the first member to provide a seal between it and the pipe, a second pipe-encircling member, and a pipe-gripping collar within the second member having an external frusto-conical surface so arranged that, upon axial movement of the second member towards the first member, the collar is contracted radially to grip the pipe.
Hitherto, in pipe couplings of this type the movement of the second member towards the first member has been effected by the two members being in screw-threaded engagement so that relative rotation between them affects the necessary axial movement of the second member. The membes are normally of hexagonal shape so that they may be securely gripped by spanners to effect the necessary relative rotation.
While such a screw-threaded arrangement is suitable for pipes of comparatively small diameter where there is easy access to the coupling, difficulties arise with pipes of larger diameter and in cases where access to the pipe coupling is restricted. In the former case large spanners are required and in either case there may be difficulty in obtaining the necessary free movement of the spanner to achieve the rotation of the coupling members. Because of these disadvantages there are certain situations, such as on board ship, where couplings of the type first referred to are not use in spite of the advantages which they may provide in other respects. The invention sets out to provide a form of coupling in which the above disadvantages may be overcome.